The present invention relates generally to chain for plastics ovens. More specifically, the present invention relates to a cart for unloading and transporting chain for plastic ovens.
In the plastics industry, it has been well-known to employ extremely large ovens to form plastic into sheets for use in a wide array of applications, such as food packaging, and the like. These plastic ovens heat the plastic and form it into wide sheets where two continuous loops of chain, positioned on opposing sides of the running sheet of plastic, effectively stretch the plastic sheet to a desired thickness for later spooling, curing, etc.
The two closed loops of chain are commonly made of individual links of chain known as "Tenter" chain which is known in the art and available from the Dornier Company in Germany. To accomplish the task of moving and stretching the continuous sheet of running plastic, each link must be extremely strong and rugged. It is not uncommon for each Tenter chain link to weigh 14 pounds each. A single closed loop chain segment on a given side of a plastics oven commonly includes 260 eight-link segments totaling 2,080 links having a gross weight of over 29,000 pounds. Periodically, as expected, this chain must be unloaded from the oven for service and repair.
In the prior art, it is common for a side door of the plastics oven to be opened to expose the Tenter chain. The loop is then broken and an eight-link segment is pulled therefrom and severed from the remaining loop of chain still remaining in the oven. This eight-link segment is manually removed from the oven and stacked onto a pallet. As can be understood, this eight-link segment weighs approximately 112 pounds and can be handled by a service technician. The remaining 259 eight-link segments are also stacked onto pallets and then sent to the repair/rebuild shop. The manually stacking of segments onto a pallet is extremely labor intensive. Not only is the job of palletizing eight-link segments a lengthy operation, it is also extremely physically demanding.
Since the individual Tenter chain links are such a critical component of a plastics oven and are extremely expensive, they are frequently unloaded and serviced to ensure that they are performing optimally. Typically, when a given loop of chain is unloaded and brought in for service, a second loop is immediately installed to avoid downtime of the oven. Essentially, it is common for at least two complete sets of Tenter chain, per side, to be used and rotated throughout the operation life of the oven. As a result, it can be understood that the aforementioned problems associated with unloading Tenter chain also apply to transporting the chain back to the oven after service and re-loading the chain into the oven. Overall, the current process of unloading, transporting and reloading Tenter chain is extremely burdensome and inefficient.
No attempts have been made in the prior art to streamline the chain transport problem discussed above. Larger than eight-link segments may be broken off and palletized to save some time, but in general, the entire process remains burdensome and inefficient. Due to the demand for a system for unloading, transporting and re-loading Tenter chain, it is desirable for a Tenter chain transport system to be efficient and not physically demanding. Further, it is also desirable for such a chain transport system to require much less time than prior art systems to unload and transport large numbers of Tenter chain links. Further, it is desirable that such a chain transport system require fewer people to unload and transport the chain link segments.